Credit Card Reader activates Winamp
 

I just got a Square Credit Card reader for my Samsung Galaxy S Captivate. The first time I plugged it in (goes in the audio jack) and unplugged it, all of a sudden it started playing music from my playlist (which I quickly erased).

While the status bar didn't show anything, I brought up Winamp since it is my default player. The control bar showed the song playing but the "play" button wasn't active/didn't show as "pause" to stop it. I clicked play and then pause and then it quit playing.

Any thoughts on how to stop this action?